A numerical Hartree self-consistent field calculation of an autoionization resonance parameters for a doubly excited 2s^2, 3s^2, and 4s^2 states of He atom with a complex absorbing potential

The self-consistent Hartree-Fock equation for the He atom is solved using the pseudospectral method. The Feshbach- type autoionization resonance parameters for doubly excited 2s2, 3s2, and 4s2 IS states of He have been determined by adding a complex absorbing potential to the Hamiltonian. The Riss-Meyer iterative and Pad6 extrapolation methods are applied to obtain reliable values for the autoionization resonance parameters, which are compared to previous results in the literature.